This invention is in the field of mosquito and/or flea control.
In one aspect the invention relates to a plant which has mosquito and/or flea repellent properties.
In another aspect the invention provides an oil extract from the said plant which, in various forms and by various means, may be used as a mosquito and/or flea repellent.
A mosquito""s and/or flea attraction to warm blooded animals is partly by body warmth and also by carbon dioxide as expelled breath. Certain vaporous substances, such as essential oils, are able to block the carbon dioxide message thus falsely indicating to the mosquito and/or flea that the animal is simply a source of warmth like a light globe or candle.
Many species of plants, such as tea-tree (Leptospermum SP), are known to produce a large amount of complex mixtures of oils which are stored in their tissues.
It is an object of this invention to isolate and characterise a true breeding clone of a plant which, by virtue of its oil content, is able to act as a mosquito repellent.
Such mosquito and/or flea repellency can occur by oxidisation of the oils from the leaves and stems of the plant directly into the surrounding atmosphere. Alternatively the oils may be extracted from the plant tissue and this extract may be used in aerosol sprays or dispersants or in pharmaceutical preparations suitable for direct topical application to the skin of a human or other warm blooded animal.
The present invention provides:
a plant of the Genus Leptospermum species liversidgei which is able to block the carbon dioxide message to mosquitoes and/or fleas within the vicinity of its locus.
The present invention also provides a crude or refined essential oil extract from the said plant.
Another aspect of the invention provides a method for repelling mosquitoes and/or fleas comprising the cultivation of the said plant.
A further aspect of the invention provides another method for repelling mosquitoes and/or fleas comprising the use of the said essential oil extract from the said plant.
It is advantageous if the plant according to the invention, is aesthetically attractive and thus is suitable as an ornamental plant. The most preferred morphological characteristics are those given in FIGS. 1 and 2.
The oil which is most suitable for the purpose of the invention is citronellal however the citronellal analogues isopulegol and pulegol are also effective.
A plant according to the invention will have a citronellal and/or analogue content which falls substantially within the range of at least 55-95% of total extractable volatile oil content. (Throughout this specification, the proportions of oil content are expressed as area percentages measured as areas under peaks by gas-chromatography.)
The oil content may exhibit seasonal and/or regional variation but it is preferred that it will be at least 70% citronellal and/or analogues.
This content may be made up of amounts of citronellal, isopulegol and pulegol which fall substantially within the ranges of 59-68%, 9-14% and 0-5% respectively.
The most preferred clone of the plant which exhibits the desired morphological features and oil content is genetically characterised by the Randomly Amplified Polymorphic DNA (RAPD) fragment analysis given in FIG. 3.
An essential oil mixture may be extracted from the tissues of the plant according to the invention.
It is preferred that the extracted oil will contain 55-95% citronellal and/or the citronellal analogues isopulegol and pulegol. It is more preferred that the oil will comprise at lease 70% citronellal and/or analogues.
The most preferred embodiment of this aspect of the invention is an essential oil extract from the plant identified by the RAPD fragment analysis given in FIG. 3.
The plant according to the invention may be used as a mosquito repellent by planting one or more shrubs in either outdoor or indoor situations. Mosquito and/or flea repellency preferably occurs by oxidisation into the surrounding air of oils from the leaves and stems of the plants. Alternatively the leaves may be manually crushed or bruised to promote the efflux of the oils.
An extracted oil from the plant according to the invention may be used in a method for repelling mosquitoes and/or fleas. The oil may be vaporised by any means known in the art such as a thermal vaporiser (for example an oil burner or other heating device) or by impregnation into a vapour dispersion block or gel.
Alternatively, the oil may be applied directly to the skin or clothing of a human or animal. In this case it is preferred that the oil is mixed with appropriate pharmaceutical carriers or excipients which make it suitable for topical application. Examples of such preparations include soaps, alcohol based creams or lotions, oil-based creams and zinc-based creams.
These methods for repelling mosquitoes may be used individually or in combination with each other.